1. Field of the Invention
The present invention relates to lathe spindle units and lathe apparatuses.
2. Description of the Related Art
Lathe apparatuses, which are typical machining tools, are already well known. A lathe apparatus has: a lathe spindle unit that is provided with a rotatable spindle having a holding section for holding a work piece, and a drive source for rotatively driving the spindle; a base for supporting the lathe spindle unit; and a tool for machining the work piece. (See, for example, JP 07-100711A.)
With such lathe apparatuses, when the spindle is rotatively driven by the drive force of the drive source, the work piece that is held by the holding section of the spindle is rotated, and the rotating work piece is cut and machined by the tool.
The lathe spindle unit described above generally has a mechanism for transmitting the drive force of the drive source to the spindle through gears or the like. However, lathe spindle units having such a mechanism have, for example, the following problems. That is, there is a possibility that a desired machining precision cannot be obtained due to backlash that occurs in the gears, for example. There is also the problem that the spindle becomes long in its rotation-axis direction due to a pulley being provided at the end, in the rotation-axis direction, of the spindle, resulting in the unit becoming large.